# Copyright (c) 2009, Digital Enterprise Research Institute (DERI),
# NUI Galway
# All rights reserved.

# author: Cosmin Basca
# email: cosmin.basca@gmail.com

# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#    * Redistributions of source code must retain the above copyright
#      notice, this list of conditions and the following disclaimer.
#    * Redistributions in binary form must reproduce the above copyright
#      notice, this list of conditions and the following disclaimer
#      in the documentation and/or other materials provided with
#      the distribution.
#    * Neither the name of DERI nor the
#      names of its contributors may be used to endorse or promote  
#      products derived from this software without specific prior
#      written permission.

# THIS SOFTWARE IS PROVIDED BY DERI ''AS IS'' AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL DERI BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
# OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
# PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
# LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
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# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
# OF THE POSSIBILITY OF SUCH DAMAGE.

# -*- coding: utf-8 -*-
__author__ = 'Cosmin Basca'

# the rsf way
#from rdf.graph import Graph, ConjunctiveGraph
#from rdf.term import URIRef, Literal, BNode, RDF, RDFS
#from rdf.namespace import Namespace


# the rdflib 2.4.x way
from rdflib.Namespace import Namespace
from rdflib.Graph import Graph, ConjunctiveGraph
from rdflib.URIRef import URIRef
from rdflib.BNode import BNode
from rdflib.Literal import Literal
from rdflib.RDF import RDFNS as RDF
from rdflib.RDFS import RDFSNS as RRDFS
import logging

from surf.query import Query

class QueryTranslator(object):
    '''The `QueryTranslator` class is responsible with the translation of the query
    to the appropriate query language in use. One must extend the class and override the
    :meth:`surf.query.QueryTranslator.translate` method'''
    def __init__(self, query):
        self.__query = query
        if not self.__query.query_type:
            raise ValueError('No query type specified')
    
    def set_query(self,query):
        if type(query) is Query:
            self.__query = query
        else:
            raise ValueError('query object must be of Query type')
    query = property(fget = lambda self: self.__query,
                     fset = set_query)
    '''the `query`, a :class:`surf.query.Query` instance'''
    
    def translate(self):
        '''translates the `query` to the appropriate query language
        
        note: **must** be overriden by subclasses'''
        return ''
    
